This invention relates to an apparatus for transferring stacks of flexible products from one elevation to another while creating a fold in the stack. More particularly, the apparatus of the present invention is useful for transferring stacks of flexible products such as bags within a bag sealer.
The machinery used for the production of individual flexible web products such as plastic containers and bags is well known in the art. U.S. Pat. Nos. 4,976,673 and 5,014,978, for example, disclose the type of equipment that is used for producing individual flexible bags. Generally, the machinery includes a large diameter rotating drum which contains multiple heated wire severing and sealing elements positioned in grooves located within the outer periphery of the drum for severing and sealing a continuous web of thermoplastic material which has been folded upon itself to form two plies. The individual bags, are formed by severing portions of the thermoplastic material. The severed areas become side seams for the bags and are typically sealed at the same time as they are severed by the use of the heated wire elements. The individual bags are retained on the drum by a vacuum arrangement as the drum rotates.
The individual bags formed on the large rotating drum are taken from the drum by a smaller transfer drum, also suitably equipped with vacuum. The vacuum on the bags on the large drum is relieved at an appropriate point, and the bags fall onto the smaller drum where the bags are held in position by vacuum. At an appropriate point, the vacuum is released and the individual bags are pulled off the smaller drum by an orbital packer or similar device.
The orbital packing device is provided with a set of packer fingers which move in a circular path in precise timing with the smaller drum so that the fingers remove successive bags, which are typically separated on the drum approximately a nominal 1/8 inch (0.003 m) from each other, from the smaller drum and stack the bags horizontally on a stacking or delivery table against a backstop.
At a precise time, count fingers pivot between a first position which is completely out of the stream of bags into a position between bags to separate the stack of bags into the desired count. The delivery table may be lowered to permit a first clamp assembly to clamp the stack of bags and transfer the stack to further conventional equipment for packaging the bags.
The first clamp assembly may be, for example, a horizontal transfer apparatus including a set of clamping jaws for grasping the stack of bags as described in U.S. Pat. Nos. 4,284,301 and 4,588,070. The horizontal transfer apparatus is used to transfer, in a horizontal alignment, the stack of bags to the surface of a support platform where the stack of bags are laid on the top surface of the support platform for further handling.
Once the stack of bags is delivered to the support platform, the stack of bags is usually at a position directly above a dispenser loading station and a second clamping assembly. The second clamping assembly is raised up to the stack of bags by a cam actuated elevator plate, and then the stack of bags is clamped with a pair of bag clamp fingers which grip the stack at its approximate centerline. Then the cam actuated elevator plate, to which said bag clamp fingers are mounted, lowers the stack from the support platform through a pair of folding guides which places a first fold into the stack (generally, the stack is folded in half) as the stack moves down to a position just below the guides.
The guides restrain the stack until an awaiting turret assembly positions a turret clamp having a pair of clamping jaws which clamp the bottom of the folded stack, wherein the bag clamp fingers on the second clamping assembly are released. The turret assembly begins to index 180 degrees from its dwell position. As the turret assembly indexes, the once-folded stack of bags receives a second fold as the clamped stack of bags passes a folding guide or shroud. The shroud maintains the second fold until the turret assembly stops rotating. The turret clamps are then lowered into an awaiting dispenser, via a cam actuated carton load mechanism, at a position below the turret clamps. The final orientation of the bags in the dispenser is in the form of a twice-folded stack.
The above conventional machinery as a whole, sometimes referred to a "bag sealer apparatus", is well known in the art such as one designed and built by Paper Converting Machine Company (PCMC). The second clamping assembly or cam actuated elevator plate, to which bag clamp fingers are mounted, discussed above, currently used in a bag sealer apparatus is sometimes referred to as a "first fold bag clamping apparatus" which is used for transferring stacks of flexible products from one elevation to another, in vertical alignment, while creating a fold in the stack.
The current first fold bag clamping apparatus uses four separate air actuated devices to operate four separate clamp fingers; the use of four separate actuators has its drawbacks. Using the current first fold bag clamping apparatus, when one actuator fails the whole bag producing and packaging system described above has to be shut down to fix the actuator that fails. Sometimes, the separate actuators used do not actuate simultaneously which also necessitates a shut down of the whole system to correct this malfunction. Furthermore, when one of the actuators does not allow a clamping finger to clamp the stack of bags with an adequate amount of force, again, the entire system must be shut down to adjust the actuator accordingly. When the separate sets of clamping mechanisms do not actuate simultaneously or adequately to clamp the stack of bags, jamming is not uncommon in prior art devices. Such jamming also results in shutting down the apparatus and bag making process entirely.
With prior art devices, there is an average of about 5 failures per bag sealer a month related to the actuators of prior art devices; and rebuild time (fixing time) for the actuators is normally about 2 hours, thus there is a need for a first fold bag clamping apparatus which operates with less failures and less maintenance.
To overcome the above-mentioned disadvantages of the prior art first fold bag clamping apparatuses, it is desired to provide an improved and less complicated first fold bag clamping apparatus.